EXPERIMENTAL HARVESTS OF MACROALGAE ALONG THE OREGON COAST
WITH AN ANALYSIS OF ASSOCIATED EPIPHYTIC DIATOM COMMUNITIES
by
JOHN J. YOUNG
A THESIS
Presented to the Department of Biology
and the Graduate School of the University of Oregon
in partial fulfillment of the requirements
for the degree of
Master of Science
December 2003
11
"Experimental Harvests of Macroalgae along the Oregon Coast with an Analysis of
Associated Epiphytic Diatom Communities," a thesis prepared by John 1. Young in
partial fulfillment of the requirements for the Master of Science degree in the Deparment
of Biology. This thesis has been approved and accepted by:
..
Dr. L nda Shapirp, Chair the Examining Committee
Dat
Committee in Charge:
Accepted by:
Dr. Lynda Shapiro, Chair
Dr. Alan Shanks
Bryan Herczeg
Dr. Steve Murray
....:>
Dean of the Graduate School
© 2003 John J. Young
III
IV
An Abstract of the Thesis of
John J. Young
in the Department of Biology
for the degree of
to be taken
Master of Science
December 2003
Title: EXPERIMENTAL HARVESTS OF MACROALGAE ALONG THE OREGON
COAST WITH AN ANALYSIS OF ASSOCIATED EPIPHYTIC DIATOM
COMMUNITIES
Approved: -ll~........rJ..-A~~Ib...tI~,--..."."."""",,==--------
I Dr. Lynda Shapiro
Macroalgae (seaweeds) are the basis of a major global industry. Oregon, however,
does not allow the commercial harvest of its seaweeds. This study looked at within- and
between-year recoveries of five species of macroalgae following harvest. Three
experiments compared seasonal harvests, removal methods, and removal amounts. Only
Alaria marginata Postels et Ruprect regained pre-harvest lengths within one year.
However, recovery was evident in all five species one year after treatments. These results
suggest the possible sustainable harvest of Oregon's algal resources. Additionally, the
diatom community epiphytic on Mastocarpus papillatus (C. Agardh) Kutzing was
,~
chronicled between May and September 2002. Diversity peaked in May when abundance
was lowe.st and reached a low in July when abundance was highest. Cocconeis scuttelum
Ehrenberg was the most common epiphytic taxon. Characterizing the epiphytic
community provides an additional metric for assessing macroalgal recovery.
II
I~
CURRICULUM VITAE
NAME OF AUTHOR: John J. Young
GRADUATE AND UNDERGRADUATE SCHOOLS ATTENDED:
University of Oregon
Aquinas College
Grand Rapids Community College
DEGREES AWARDED:
Master of Science in Biology, 2003, University of Oregon
Bachelor of Science in Biology, 2001, Aquinas College
Associate of Arts, 1998, Grand Rapids Community College
AREAS OF SPECIAL INTEREST:
Ecology
Phycology
Resource Management
PROFESSIONAL EXPERIENCE:
Research Assistant, Oregon Institute of Marine Biology, Charleston, 2001-2003
Teaching Assistant, Department of Biology, University of Oregon, Eugene, 2002
GRANTS, AWARDS AND HONORS:
Neil Richmond Fellowship, 2003
v
I
VI
ACKNOWLEDGMENTS
I wish to thank my advisor, Dr. Lynda Shapiro, for giving me the opportunity to
conduct this research and providing insightful guidance. I also extend my gratitude to my
committee members, Dr. Alan Shanks, Bryan Herczeg, and Dr. Steve Murray, whose
expertise made significant contributions to the experiments and manuscript. A sincere
thanks is deserved by Barbara Butler for always keeping me current with the scientific
literature. Mike Berger and Dr. Richard Emlet shared invaluable statistical knowledge. I
am indebted to the graduate students of OIMB for all the field assistance and diversions
that made completion of this work possible. Finally, I need to thank Holli Charbonneau
and Sue Young for never doubting me even when I doubted myself. This research was
partially funded by the NOAA Office of Sea Grant and Extramural Programs, U.S.
Department of Commerce, under grant number NA16RG1039 (project number NA084M),
and by appropriations made by the Oregon State legislature. The views expressed herein
do not necessarily reflect the views of any of those organizations. Additional support was
provided by Oregon Parks and Recreation Department.
V. CONCLUDING SUMMARY 71
1. GENERAL IN1RODUCTION 1
II. EXPERIMENTAL HARVESTS OF FIVE SPECIES OF
MACROALGAE ALONG THE ORGON COAST 3
Vll
Page
TABLE OF CONTENTS
Alaria marginata 46
Laminaria setchellii 47
Fucus gardneri 48
Mastocarpus papillatus 48
Mazzaella splendens 49
Bridge 51
Introduction 3
Materials and Methods 5
Results 11
Discussion 31
Bridge 44
III. PROPOSED MANAGEMENT RECOMMENDAnONS FOR THE
HARVEST OF FIVE MACROALGAL SPECIES ALONG
THE OREGON COAST 45
IV. ANALYSIS OF THE EPIPHYTIC DIATOM COMMUNITY UPON
THE MACROALGA MASTOCARPU PAPILLATUS
(C. AGARDH) KUTZING 52
Introduction 52
Materials and Methods 54
Results ./ 59
--Discussion 66
Chapter
B. SUMMARY OF EPIPHYTIC DIATOM SPECIES ABUNDANCE
OVER THE 2002 GROWING SEASON 86
APPENDIX
A. STATISTICAL TABLES FROM CHAPTER II 73
REFERENCES 91
Chapter I 91
Chapter II 91
Chapter III 95
Chapter IV 95
Vlll
PageChapter
Figure
LIST OF FIGURES
Page
IX
1. Selected Study Sites Along the Oregon Coast 6
2. Season of harvest experiments for Alaria 12
3. Re~overy ofAlaria from Hooskanaden Creek after the Season
ofHarvest Experiments ~ 13
4. Recovery ofAlaria from South Cove after the Season of Harvest
Experiments 15
5. Season of Harvest Experiments for Laminaria 16
6. Recovery ofLaminaria from Hooskanaden Creek after the Season
. ofHarvest Experiments 17
7. Recovery ofLaminaria from South Cove after the Season of
Harvest Experiments 18
8. Season ofHarvest Experiments for Fucus 20
9. Recovery ofFucus from Lone Ranch Creek after the Season
, ofHarvest Experiments 21
10. Season of Harvest Experiments with Mastocarpus at
Lone Ranch Creek 22
11. Season of Harvest Experiments with Mazzaella at
Hooskanaden Creek 24
12. Recovery ofAlaria from Hooskanaden Creek after
the Selective/ Method ofHarvest Experiments 25
v'
13. Recovery ofAlaria from South Cove after the
Selective/ Method of Harvest Experiments 27
14. Recovery ofLaminaria from Hooskanaden Creek after the
Selective/ Method of Harvest Experiments 28
15. Recovery ofLaminaria from South Cove after the
Selective/ Method of Harvest Experiments 29
16. Recovery of Fucus from Lone Ranch Creek after the
Selective/ Method of Harvest Experiments 30
17. Recovery of Mastocarpus from Lone Ranch Creek after the
Selective/ Method of Harvest Experiments 32
18. Recovery of Mazzaella from Hooskanaden Creek after the
Selective/ Method of Harvest Experiments 33
19. Location of Lone Ranch Creek 55
20. Correlation between the In of Surface Area and the
Dry Weight of Mastocarpus papillatus 57
21. Mean Numbers of Cocconeis scuttelum Valves Counted
per Sample 60
22. Epiphytic Diatom Patterns over the 2002 Growing Season 62
23. Epiphytic Diatom Patterns over Four Consecutive Days in 2003 63
24. Epiphytic Community Patterns in 2002 64
25. MDS Plots of the Epiphytic Communities from 2003 65
x
Table
LIST OF TABLES
Page
Xl
1. Recommended Management Strategies for the Harvest of
Five Macroalgal Species of Oregon 50
2. Man-Whitney U Tests Comparing Mean Lengths of Harvested
and Unharvested Algae in August 2002 74
3. ANOVA Source Tables Comparing Biomass of Season of
Harvest Plots in 2002 76
4. ANOVA Source Tables for Total and Germling Holdfast
Density of Season of Harvest Plots in 2003 78
5. Factorial ANOVA Source Tables for Total and Germling
Holdfast Density of SelectivelMethod of Harvest Plots
in 2003 81
6. Kruskal-Wallis Test Results from SelectivelMethod of Harvest
Plots of Laminaria setchellii at Hooskanaden Creek 84
7. ANOVA Source Tables for Plot Density of SelectivelMethod of
Harvest Plots in 2003 85
8. Summary of the Mean Relative Abundance of Mastocarpus
Diatom Epiphytes Collected and Counted During the
2002 growing season 87
v·
1CHAPTER I
GENERAL INTRODUCTION
Marine algae are harvested commercially worldwide resulting in a multi-billion
dollar industry annually (Zemke-White and Ohno 1999). Macrophyte harvesting along
the west coast of the United States is included in these figures. Oregon, however, does
not permit the commercial harvesting of its algal resources due to a lack of knowledge
regarding seaweed recovery. Yet, with the potential for commercial harvest, it is
necessary to examine the effects harvesting would have on Oregon's seaweed.
Studies that have experimentally tested the effects of harvesting on macrophyte
populations provide the best basis for management plans (Nelson and Conroy 1989; Ang
et al 1996; Griffen et al 1999; Lavery et al 1999). Chapter II of this thesis describes
various harvest experiments to test the effects of (1) harvesting during different seasons,
(2) different harvest amounts and (3) different removal methods on five perennial species
of macroa1gae. The data from these experiments are used in Chapter III to recommend a
management strategy for the tested species. This work will be useful in drafting a
management plan for the regulation of seaweed harvest in Oregon.
Chapter IV compares the epiphytic diatom community upon Mastocarpus
papillatus (c. Agardh) Ktitzing, one of the species used in the harvest study, over a
growing season. Epiphytic diatoms are used as environmental indicators because the
2silicified frustules are taxonomically distinct, easily preserved, and variations in
community composition track environmental conditions (Christie and Smol 1993). This
study provides baseline data on M. papillatus epiphytes that will aid in assessing recovery
from disturbance events such as harvesting. The chapter also provides basic information
on epiphyte diatom communities in the rocky intertidal.
3CHAPTER II
EXPERIMENTAL HARVESTS OF FIVE SPECIES OF MACROALGAE
ALONG THE OREGON COAST
Introduction
The harvest of seaweed is a major industry worldwide. Global harvesting of
seaweed for use as food products is estimated to value over 3.6 billion US dollars
annually (Zemke-White and Ohno 1999). Additionally, the annual estimated value of the
production of phycocolloids (i.e., alginates, agar, and carrageenan) from seaweed is 2.6
billion US dollars (Zemke-White and Ohno 1999). These data do not include seaweed
harvested for medicinal purposes because accurate figures are difficult to compile.
Aquaculture is an important method of producing seaweed resources accounting for 52%
of commercial production (Zemke-White and Ohno 1999). The remaining 48% is,
therefore, collected from wild stocks. Due to the large scale of world seaweed harvest,
studies have experimentally exMnined the impacts of harvesting activities on macrophyte
populations (Nelson and Conroy 1989; Ang et a11996; Griffen et a11999; Lavery et al
1999). Based on these studies, management plans have been developed (Westermeier et
a11987; Westermeier et a11999; Vasquez and Vega 2001).
4The harvesting of marine algae for human use has been recorded before the 14th
century in Portugal. This practice began by collecting beach cast seaweed for use as
fertilizer. Today, the exploitation of its seaweed in Portugal continues with Portugal
being the world's fifth largest agar producer (Santos and Duarte 1991). China, France,
u.K., Korea, Japan, and Chile are responsible for 90% of the world's seaweed
production.
Comparatively, the US is not a major contributor to world seaweed production
(Zemke-White and Ohno 1999). Furthermore, with the exception of Macrocystis
harvest, the west coast of the US has a negligible production of commercial seaweed
(Merrill and Waaland 1998; Zemke-White and Ohno 1999). Most harvesting that does
occur on the Pacific Coast of the US is by small cottage industries which take relatively
small amounts of seaweed from the wild (Zemke-White and Ohno 1999). Yet, since
1984 the production of commercially important seaweeds has grown by 119% (Zemke-
White and Ohno 1999). The increasing value of seaweed as a food and industrial
resource makes large-scale harvesting in the Pacific States likely in the near future.
To remove marine algae from the Oregon intertidal zone requires a permit issued
by the state. Historically, the issuing of these permits has been rare. Recently the state
has, however, received an increase in requests for such permits. Permits are also required
to harvest marine algae in the states of Washington, Alaska, and California. With the
potential for a growing industry of seaweed harvest in Oregon, it is necessary to examine
the effects harvesting will have on wild stocks of marine algae.
5This study was designed to assess the effects of commercial harvesting on algal
resources and to provide information useful in drafting a management plan for seaweed
harvesting in Oregon. The study had two goals: to assess (1) the within and between year
recovery of seaweeds harvested during different seasons and (2) the recovery in
subsequent years following different removal methods and amounts. Within-year
recovery was defined as reaching pre-harvest lengths or biomasses and second recovery
was defined as reaching pre-harvest plot density.
The five species chosen for study were Alaria marginata Postels et Ruprecht,
Laminaria setchellii Silva, Fucus gardneri Silva, Mastocarpus papillatus (c. Agardh)
Ktitzing, and Mazzaella splendens (Setchel et Gardner) Fredericq in Hommersand,
Fredericq et Freshwater. All five species are perennials and are harvested either for food
or dietary supplements (Abbott and Hollenberg 1976; Zemke-White and Ohno 1999).
They are found in the mid to low intertidal zone of rocky shores all along the Oregon
coast. Species will be referred to by genus henceforth.
Materials and Methods
Three sites were chosen for experimentation. South Cove (43°18.13'N,
124°23.91 'W) is part of Cape Ango State Park, Oregon, USA, Hooskanaden Creek
(42°13.17'N, 124°22.73'W) and Lone Ranch Creek (42°05.98'N, 124°20.82'W) are
located in Samuel H. Boardman State Park, Oregon, USA (Fig. 1). Laminaria, Alaria,
and Mazzaella were harvested from Hooskanaden Creek. Mastocarpus, and Fucus were
"
6Pacific
Ocean
Pacific
Ocean
OREGON
Figure 1: Selected Study Sites Along the Oregon Coast. Alaria and Laminaria were
collected from South Cove and Hooskanaden Creek. Fucus and Mastocarpus were taken
from Lone Ranch Creek. Mazzaella was collected from Hooskanaden Creek.
studied at Lone Ranch Creek. Experiments with Laminaria and Alaria were repeated at
South Cove. All three sites are characterized by rocky substrata.
Preliminary studies at the southern sites (i.e., Hooskanaden Creek and Lone
Ranch Creek) were done by randomly placing a 0.5M x 0.5M quadrat along transects
parallel to shore and estimating species abundance via percent cover. Transects were
placed at tidal levels supporting the zonal distribution of each individual species. Algal
cover at Hooskanaden Creek averaged over 90%. Alaria and Laminaria were the
dominant species in these measurements. Mazzaella was abundant at higher tidal
elevations at Hooskanaden Creek. Lone Ranch Creek was estimated to have about 50%
algal cover with Fucus and Mastocarpus being the most abundant.
Permanent transects and marked plots were placed through or in areas densely
covered by the target species because such areas are chosen for harvesting. Bolts and
bolt anchors drilled into the rock marked the endpoints of permanent transects. Some
transects passed through areas covered with two target species. Areas along these
transects were selected as harvest plots if they were densely covered (approximately
100%) with one target species. A numbered tag anchored to the rock with a screw and
screw anchor marked the center of each plot. Quadrats were centered on the tag and an
attached compass assured one edge of the quadrat was parallel to the transect. This
allowed exact return to marked areas. Plots of Laminaria and Alaria were 0.5m x 0.5M
and plots of Fucus, Mastocarpus, and Mazzaella were 0.2M x 0.2M.
Season of Harvest Experiments
7
8Experimental harvests were conducted in May and June to compare the effects of
harvesting during the spring and summer seasons, respectively. Three experimental plots
were randomly assigned for each seasonal harvest. The first experiment occurred during
the spring tide series between 25 and 30 May 2002. Harvests were performed on target
species at all sites with the exception of Mazzaella and Alaria at South Cove. Large
swells and high tides prevented these harvests. A summer harvest was performed on all
species at all sites between 24 and 29 June 2002.
Experimental plots of Alaria and Laminaria had all harvestable quality plants
(>50cm) marked through the stipes with numbered spaghetti tags (Floy Tag & Mfg., Inc.
Seattle, Wa). Tagged plants were cut 6-10 cm above the meristems, and lengths
recorded. Cutting above the meristems was chosen for Laminaria and Alaria because
both show intercalary growth (Abbott and Hollenberg 1976). Furthermore, sporophylls
of Alaria were spared. Fucus, Mastocarpus, and Mazzaella all possess apical meristems
(Abbott and Hollenberg 1976), therefore, plants were cut 2-5 cm above the holdfast. All
harvestable plants in experimental plots were tagged, cut and measured. Harvested plants
were remeasured monthly during spring tides until August of 2002. Control plots (n=4 or
more) were randomly assigned for each species at each site. Two of the control plots
were tagged, measured, but left-uncut. The other control plots were left untouched for
subsequent year comparison. All tagged plants were then measured monthly through
August 2002 during spring tides. All algae in experimental and tagged control plots were
collected during the first spring tide in August 2002. Within-season controls were then
9used as experimental August harvest plots in subsequent years. Collection was done
according to the methods described above.
Selective/Method of Harvest Experiment
Plots of the same sizes were randomly selected along the same transects used in
the season of harvest experiments. Selected plots were randomly assigned a treatment of
either 25% frond removal, 25% entire alga removal, 50% frond removal, 50% entire alga
removal, or control. All treatments were replicated three times. In plots chosen for frond
removal, the algae were cut in the same manner as in the season of harvest experiments.
Plots chosen for entire alga removal had the designated number of algae removed from
the substrate by prying off their holdfasts. Controls were left undisturbed and used for
reference in all experiments during subsequent years.
Plots of A/aria and Laminaria had all holdfasts counted in the quadrat prior to any
removal. Then all harvestable quality plants (>50cm) were counted. Either 50% or 25%
of plants >50cm were removed according to the treatment assigned. In plots where an
even number could not be taken, we rounded up to the next whole number. Plots of
Fucus, Mastocarpus, and Mazzaella were not counted prior to removal. These plots were
usually 100% full of the target species. A quadrat equally divided into four sections was
used and algae were removed from one or two squares depending on the assigned
treatment. Algae were always removed from the same squares to ensure consistency.
Experiments were performed on A/aria and Laminaria in both Hooskanaden
Creek and South Cove over the first spring tide series in July 2002. The experiments
10
were performed on Mazzaella, Fucus, and Mastocarpus papillatus during the second
sping tide series in July 2002.
Experimental and control plots from both experiments were monitored during
spring tides beginning in April 2003 through August of 2003. Recruitment in plots of
A/aria, Laminaria, and Fucus was measured by counting the total number of holdfasts in
the quadrat and the number of germlings. A/aria plants were scored as germlings if no
sporophylls were present (typically < 50cm). Laminaria < 50cm were considered
germlings and Fucus plants < 1cm in length were scored as germlings (Speidel et al.
2001). Percent cover was visually estimated with a subdivided quadrat for Mazzaella and
Mastocarpus.
Collected algae were rinsed in freshwater to remove all epifauna previous to
recording wet weight. The rinse water was passed through 150/-lm mesh and collected
epifauna was preserved and cataloged. Algal samples were placed in a drying oven set at
60°C for 14 days prior to measuring dry weight. Aliquot samples from dried material of
approximately 0.5g were placed in a muffle furnace set at 500°C for 14hrs to measure ash
free dry weight (AFDW) and organic dry weight of the samples. Biomass was estimated
by measuring the mass lost from the aliquot after heating and back calculating to
determine organic dry weight of the plot. This figure was then multiplied by a constant
derived from plot size to estimate organic cry weight per square meter.
Non-parametric Man-Whitney V-tests were used to compare final lengths of May
and June harvested plants to control lengths. Within site biomasses and second year
density data from the season of harvest experiments were compared with one-way
11
ANOVAs. When control replication was adequate (> 4), data from the selective
harvest/method of removal experiments were analyzed using a factorial ANOVA design
with method of removal (frond or entire alga) and amount of removal (25%, 50%, or
control) as factors. One-way ANOVAs were used when a factorial design wasn't
possible because control plot loss. A post-hoc Bonferroni test was performed on all
significant results. All data were square root transformed if Cochran's C-test for
homoscedasticity was significant. Furthermore, if transformations still failed Cochran's
C-test, a non-parametric Kruskal-Wallis test was used. Statistical analyses were
performed using the software package STATISTICA 6.0 (Statsoft).
Results
Season of Harvest Experiments
A/aria marginata
The lengths of plants harvested in May from Hooskanaden Creek were not
significantly different from the lengths of control plants when the experiment ended in
August (Fig. 2a; p=0.620; Appendix A: Table 2). The same result was obtained when
June harvested plants were compared to controls (p=0.522; Appendix A: Table 2).
However, a June harvest only, performed at South Cove (Fig. 2b) showed a significant
difference between lengths at the end of August (p<.OOI; Appendix A: Table 2).
The ANOVA indicated that there were no significant differences between the
final biomasses of experimental and control plots (Fig. 3a; p=0.591; Appendix A: Table
12
-0- May Harvest
-0- June Harvest
-T- Control (No Harvest)
3.0
2.5
,-..
'"....E
v 2.0g
.0
'C
"0 1.5~
......
0
-5 1.0
/>IJ
c::
<i.l
.....l
0.5
0.0
140 160 180 200 220
a
240
-0- June Harvest
-T- Control (No Harvest)
3.0
2.5
,-..
'"....~ 2.05
.0
'C
"0 1.5~
......
0
-5 1.0/>IJ
c::
<i.l
.....l
0.5
0.0
170 180 190
Julian Day
200
Julian Day
210 220
b
230
Figure 2: Season of Harvest Experiments for A/aria. Data points show the mean midrib
lengths of A/aria from (a) Hooskanaden Creek and (b) South Cove. Error bars show
one standard error from the mean.
13
a
Control
t
June Final
Treatment
May Final
60
• Total Holdfasts
50
~ 40
<ii
"."os:
30
t
'i3
.5
...
0
.. 20
10
bi
0
May June August Control
Treatment
50
0 Germlings
40
~
<ii 30
"."os:
'i3
.5
1
... 200
..
10 !
-,,-- c
0
May June August Control
Treatment
<'l~5oo ,..---------------------,
~
*E
oe!l400
<l)
~
C
~3oo
°2
co
e.n
0200
~
6b
~1oo
i2
CO
E
o
iii
Figure 3: Recovery of Alaria from Hooskanaden Creek after the Season of Harvest
Experiments. Within-year recovery (a) is represented by plot biomass. Second year
recovery is shown by total(b) and germling(c) holdfast density. Error bars show one
standard error from the mean.
14
3). Total and germling holdfast counts per plot in 2003 also showed no significant
differences between all treatments (Figs. 3b and 3c; p=0.731 and p=0.847, respectively;
Appendix A: Table 4). South Cove produced similar results (Fig. 4a and Figs. 4b and
4c).
Laminaria setchellii
The effects of both May and June harvests at Hooskanaden Creek were detected
in August. There were significant differences in overall lengths between May harvested
plants (p=O.OOl) and June harvested plants (p=0.005) and the controls (Fig. 5a; Appendix
A: Table 2). The results of the same experiments performed at South Cove also produced
significant differences (p= 0.008 and p<O.OOOl) between the two harvests and the
controls (Fig. 5b; Appendix A: Table 2).
The biomasses of all plots harvested in August were square root transformed to
satisfy the assumption of homoscedasticy required for an ANOVA (Fig. 6a; Appendix A:
Table 3).There is a significant difference between the August biomass of experimental
and control plots (p=O.OOl). Post hoc tests revealed significant differences between
control and May (p=0.006) and June (p=O.OOl) biomasses. Total and germling holdfast
counts per plot in 2003 were not significantly different (p=0.642; p=0.595) between all
treatments (Figs. 6b and 6c; Appendix A: Table 4).
In the ANOVA comparing final biomasses of plots from South Cove, treatment
effects were not significant (Fig. 7a; p=0.076; Appendix A: Table 3). Furthermore, there
15
I a
June Final Control
Treatment
• TOlal holdfasts
I f
b
June AugusL Control
Treatment
30,..-------------------,
-a 20
;:l
"0;;:
'6 15
oS
....
o~ 10
25
N- 350,..------------------,
~
*1:
b/l 300
.~
...
"0
(J 250
·c
~
o 200
I
V> 150
V>
"8
oiii 100 .L- -,-- --,,--- -------'
16
0 Gcrmlings
14
12
V>
co 10
I
;:l
"0
.;;:
'6
oS
.... 60
~
"J
C
June August Control
Treatment
Figure 4: Recovery of Alaria from South Cove after the Season of Harvest Experiments.
Within-year recovery (a) is represented by plot biomass. Second year recovery is shown
by total(b) and germling(c) holdfast density. Error bars show one standard error from the
mean.
16
240
a
220
-0- May Harvest
-0- June Harvest
----...- Control (No Harvest)
200180
2.0
1.8
1.6
r--.
VJ
.... 1.4a)
V
E
'-' 1.2
..c
en
c 1.0
a)
....l
0.8
0.6
0.4
140 160
Julian Day
-0- May Harvest
-0- June Harvest
----...- Control (No Harvest)
~
240
b
220200180160
1.1
1.0
0.9
r--.
VJ
.... 0.8a)
.....
a)
E
'-' 0.7
..c
en
c 0.6
a)
....l
0.5
0.4
0.3
140
,-- Julian Day
Figure 5: Season of Harvest Experiments for Laminaria. Data points show the mean
lengths of Laminaria from (a) Hooskanaden Creek and (b) South Cove. Error bars show
one standard error from the mean.
17
a
I
•
N~ 800 .,-------------------,
~
.*J600
C
-0
<.) 400
a
oj
bO
o 200
i§
e
!:E
Of)
gj
5
iii
May Final June Final Control
Treatment
28
• Total Holdfasts26
1
24 I..!!l 22oj::> 20 I~'B 18
.5
4-< 16
0
'*" 14
12
10 b
8
May June August Control
Treatment
18
0 Germlings
16
14
'" 12ca
::>
-0 10";;
'B
.5 8 I4-<0 6 I'*" 4
2 C
0
May June August Control
""~
Treatment
Figure 6: Recovery of Laminaria from Hooskanaden Creek after the Season of Harvest
Experiments. Within-year recovery (a) is represented by plot biomass. Second year
recovery is shown by total(b) and germling(c) holdfast density. Error bars show one
standard error from the mean.
18
~..-. 240
~ 220 I.E.!:!' 200.,~ 180
C
"to 180()
'" 140'"b1l(5 120
E 100 Ieb1l~ 80Vl~
E 60 a
0
i:O 40
May Final June Final ConLnl!
Treatment
50
• Total Holdfasts
45 IVl 40 j Ico="to 35'S:'6
.5 30
'-0
'llo 25 I20 b
15
May June AugUSl Control
Treatment
25
0 Gennlings
20
Vl
co
= 15
"to
'S:
'6
.5 I'- 100'llo I c
May June August Control
.....
Treatment
Figure 7: Recovery of Laminaria from South Cove after the Season of Harvest
Experiments. Within-year recovery (a) is represented by plot biomass. Second year
recovery is shown by total(b) and germling(c) holdfast density. Error bars show one
standard error from the mean.
19
were no significant differences in total and germling holdfasts between experimental and
control treatments (Figs. 7b and 7c; Appendix A; Table 4).
Fucus gardneri
In all of the tested seasons, Fucus did not grow appreciably following harvest
(Fig. 8). Plants cut in May and June both had lengths significantly shorter than control
lengths by August (p=0.002 and p=0.002, respectively; Appendix A: Table 2). The
biomass data followed a similar pattern with significant differences in total organic dry
weight (Fig. 9a; p=0.01; Appendix A: Table 3). The post hoc test revealed a significant
difference between the June harvested and control plots (p=0.02), but no significant
differences were found between the May harvest and control lengths. There were no
significant differences in total and germling holdfast counts by harvest season in the 2003
season (Fig. 9b and 9c; p=0.743 and, p=0.829, respectively; Appendix A: Table 4).
Mastocarpus papillatus
Following harvest, Mastocarpus grew little or not at all (Fig. lOa). The plants
harvested in both May and June were significantly smaller than the control plants
(p=0.004 and, p=0.014, respectively; Appendix A: Table 2). The comparisons of the
August biomasses from both experimental plots were not significantly different from that
of the control plots (Fig. lOb; p=0.805; Appendix A: Table 3). No significant differences
20
240220200
-0- May Harvest
-0- June Harvest
----....- Control (No Harvest)
180
~----~Qf-------""1:O~---o:
Il- 0 0
35
30
25
~
S
u 20
'--'
..c::
.....
01)
15s::(j)
.-:l
10
:0
5
0
140 160
Julian Day
Figure 8: Season of Harvest Experiments for Fucus. Data points show the mean lengths
of Fucus from Lone Ranch Creek. Error bars show one standard error from the mean.
N~
70~
* Ifnso0;j~1:'50
"0
u
°0 I~400'"E 30
e
!:9
i:5 20
0; aE
0iii 10
May Final June Final Control
Treatment
24
• Total Holdfasts22
20
'"
18
f
OJ
:l 16
"0
1
os:
'6 14
.5 124-<
0
~ 10 I8
6 b
4
May June August Control
Treatment
8
0 Germlings
7
'"
6
OJ
:l
::2 5
>
'6
I.5 4 04-< j0~ 32 .~ C
May June August Control
Treatment
Figure 9: Recovery of Fucus from Lone Ranch Creek after the Season of Harvest
Experiments. Within-year recovery (a) is represented by plot biomass. Second year
recovery is shown by total(b) and germling(c) holdfast density. Error bars show one
standard error from the mean.
21
25
-0- May Harvest
-0- June Harvest
.........- Control (No Harvest)
22
20
E 15
~
.c
t{,
5 10
~....l a
0
140 160 180 200 220 "0
Julian Day
N~ 35
~
*~ 30
·v
~
1:' 25
"'"u
·2
20
'" I~0E 15 I'"~
'"
10
'"
'" bE
0
ci5
May Final June Final Control
Treatment
120
100
80
... IOJ>0 80U
t'<
40 I I20 C
v
May June Augusl Contto!
Treatment
Figure 10: Season of Harvest Experiments with Mastocarpus at Lone Ranch Creek.
Within-year recovery is shown by (a) lengths and (b) biomass. Second year recovery (c)
is shown with percent cover. Error bars show one standard error from the mean.
23
(p=0.177) were found between the percent cover of the experimental plots and the control
plots (Fig. lOc; Appendix A: Table 4) in 2003.
Mazzaella sp/endens
Mazzaella failed to increase in length following the single June harvest (Fig. Ila).
Harvested thalli lengths in August were significantly smaller than control thalli lengths
(p=0.0008; Appendix A: Table 2). The August biomass of the June harvested plots were
not significantly different from the biomass of the control plots (Fig. lib, p=0.369;
Appendix A: Table 3). There were no significant differences between the percent cover
of harvested and control plots (Fig. Ilc; p=0.07; Appendix A: Table 4) in 2003; however,
there was a trend of lower percent cover in plots harvested in June.
Selective/Method of Harvest Experiment
A/aria marginata
There were no significant differences in total A/aria holdfasts whether removal
amount or method was considered (Fig. 12a; p=0.766 and p=0.433, respectively;
Appendix A: Table 5). The interaction between the two factors (removal amount and
method) also proved to be not significant (p=0.06). However, removal of fifty percent of
the frond produced the largest mean plot density, nearly twice that of the controls.
The pattern was the same for the density of germlings except there was a
significant interaction between removal amount and method of removal (Fig. 12b;
24
25
-0- June Harvest
----,- Control (No Harvest)
20
E 15
~
..c
bJJ
c 10<1.l
...J
Q 20
a
0
170 180 190 200 210 220 230
Julian Day
N 24
::s
*:c 22
Ol)
j
'0
~ 20
C
"0
u 18
'c
"Ol)o 16
'"~ 14
~
'" 12 b'"g
0
a:i 10
June Final Control
Treatment
100
80
~ 60
;> I0u~ 40
20 C
v
0
June August Control
Treatment
Figure 11: Season of Harvest Experiments with Mazzaella at Hooskanaden Creek.
Within-year recovery is shown by (a) lengths and (b) biomass. Second year recovery (c)
is shown with percent cover. Error bars show one standard error from the mean.
25
50
• Total Holdfasts
40
</)
~
::l 30
:9
;>
:.a
t::
......
4- 20
0 I'*1:: 10
I • a
0
,?\O~~ l'-\'/,~ ~ '/,~ \0\,?\O~ l'-\' GO~"
'),':>oJo ,?>i'\'{, ,:>~oJo ,?>~\,\e-
'),,:>oJo ,:>~oJo
Treatment
50
0 Gennlings
40
I</) 30~::l'".;; I:.a 20t::......4-0'*1:: 10 00
b
·10
~ '/,~ ~ '/,~ '!SO\,?\O~ ~ ,?\O~ l'-\'
'),,:>oJo '?>~\,\'{, ,:>~oJo ,?>~\,\e- GO~
'),,:>oJo ,:>~oJo
Treatment
v
Figure 12: Recovery of Alaria from Hooskanaden Creek after the Selective/ Method of
Harvest Experiments. Data points show the mean (a) total and (b) germling holdfast
density. Error bars show one standard error from the mean.
26
p=0.03; Appendix A: Table 5). Again removal of fifty percent of the fronds in the plot
yielded the greatest number of recruits. Removing 25% of the algae yielded second year
density close to that of the controls. The treatments of 25% frond and 50% entire alga
removal had the lowest plot densities. South Cove differed in that there were no
significant differences between all effects, however, the trends were similar (Figs. 13a
and 13b; Appendix A: Table 5).
Laminaria setchellii
A Kruskal-Wallis test revealed that removal of 25% of Laminaria present in plots
produced significantly lower holdfast densities one year after the treatment (Fig. 14a;
p=0.020; Appendix A: Table 6). Control plots, however, had the highest mean density of
all treatments. Removing 50% of the fronds produced the second highest mean density.
There were no significant differences in germling density across treatments (Fig.
14b; Appendix A: Table 5). The one-way ANOVA comparing total and germling
holdfast density differences at South Cove were not significant (Figs. 15a and 15b;
Appendix A: Table 7). The removal of 50% of the fronds produced a larger mean total
holdfast density than in the control plots, however, the variance was large.
Fucus gardneri
No significant treatment effects were found on total holdfast density (Fig. 16a) or
germling density (Fig 16b). Statistical tables are shown in Appendix A: Table 5.
Figure 13: Recovery of A/aria from South Cove after the Selective/ Method of Harvest
Experiments. Data points show the mean (a) total and (b) germling holdfast density.
Error bars show one standard error from the mean.
28
28
• Total Holdfasts26 I2422'"~ 20
:::l
"Cl
.;; 18
:.cJ 16s:::,.....
'+-<
0 14 I=It:: 1210 I8
a
6
~\O~o I'-\~~ o ~~ :<..\0\~\o~ ~ Co~
']..')0\0 y,~\.~e, rio .~e,
')\'J y,~\.'"
']..')0\0 ,)\)0\0
Treatment
18
0 Germlings
16
14
'" 12~
:::l
"Cl 10.;;
:.cJ
s::: 8,.....
'+-<
I0=It:: 642 b
0
~\O~o ~~~ ~\O~o ~'l,~ :<..\0\
']..')0\0 y,~\.\\e, ,)\)0\0 y,~\.\\e, Co~
']..')0\0 ')\)0\0
Treatment
v'
Figure 14: Recovery of Laminaria from Hooskanaden Creek after the Selective/ Method
of Harvest Experiments. Data points show the mean (a) total and (b) germling holdfast
density. Error bars show one standard error from the mean.
Figure 15: Recovery of Laminaria from South Cove after the Selective/ Method of
Harvest Experiments. Data points show the mean (a) total and (b) germling holdfast
density. Error bars show one standard error from the mean.
12
• Total Holdfasts
10 T
jrrJ~;:l 8"0
">:.a
I=:
>-<
4-0 6
f
0
=l:I:
4
a
2
o ~~ o ~~ i O\~~o'" ~\' ~~o'" ~\' co"'''1,,,;010 ~/..\~f(, ";1:\010 ~/..\~f(,
1,,,;010 ";1:\010
Treatment
5
0 Germlings
4
rrJ
~
;:l 3
"0
">:.a
I=:
>-<
4-0 2
0
=l:I:
f b
0
o ~~ o ~~ i O\~~o'" ~ ~~o'" ~ co"'''1,,,;010 ~",\.\~f(, ";1:\010 ~",\.\~f(,
1,,,;010 ";1:\010
Treatment
....J
Figure 16: Recovery of Fucus from Lone Ranch Creek after the Selective/ Method of
Harvest Experiments. Data points show the mean (a) total and (b) germling holdfast
density. Error bars show one standard error from the mean.
30
31
Densities were lower in treatments of 25% entire alga and 50% frond removal but not
significantly so.
Mastocarpus papillatus
None of the harvests had significant effects on percent cover of plots (Fig 17;
Appendix A: Table 7). There was a trend of 25% removal having the highest second year
cover, followed by 50% removal. Interestingly, the control treatment had the lowest
second year cover.
Mazzaella splendens
There were significant treatment effects in the percent cover of Mazzaella plots
one year after harvesting (Fig, 18; p=0.005; Appendix A: Table 7). Removing 50% of
the algae present at the holdfast produced the lowest percent cover in 2003. Post hoc
tests found significant differences between the 50% entire alga removal and all other
treatments. The treatments of 25% and 50% frond removal both had mean percent covers
not significantly different from control plots. Plots with 25% removal of the entire alga
were not assessed in 2003 because of plot marker tag loss.
Discussion
For all species examined, the season of harvest had no effect on net growth. At
the end of summer, the May-harvested treatments produced the same results as the June
100 ..,--------------------------,
32
80
~ 60
;>
o
U
~ 40
20 I
I
O..L----~---..,__---..,__---,___---+_------'
Treatment
Figure 17: Recovery of Mastocarpus from Lone Ranch Creek after the Selective/
Method of Harvest Experiments. Data points show the mean percent plot cover. Error
bars show one standard error from the mean.
33
100 -r------------------------,
80
~ 60
;>
o
U
~ 40
20
I
O-'-------.------r-------,-----.------'
25% Frond 50% Frond 50% Entire Alga Control
Treatment
Figure 18: Recovery of Mazzaella from Hooskanaden Creek after the Selective! Method
of Harvest Experiments. Data points show the mean percent plot cover. Error bars show
one standard error from the mean.
34
harvests. These comparisons lead to the conclusion that, in terms of net growth,
harvesting in Mayor June had no effect on recovery within the same year that these
species were harvested.
Alaria marginata
Alaria exhibits a typicallaminarian life-history with an alteration of generations.
Under short day conditions the macroscopic sporophyte stage releases zoospores which
settle and grow into microscopic male or female gametophytes. The gametophytes are
fertile and produce sporophytes throughout the summer (Lee 1999). Vegetative growth
in the sporophyte occurs through an intercalary meristem between the stipe and the frond
(Buggeln 1974; tom Dieck 1991). The sporophyte frond is collected by harvesters.
Harvesting Alaria as early as May and as late as August was unlikely to have
significant effects on' reproduction and recruitment. This is supported by the lack of
significant differences between total and germling holdfast densities between treatment
and control plots one year after treatments. Pfister (1992) found removal of the
vegetative frond throughout the growing season significantly decreased the reproductive
investment of Alaria nana yet, reproductive investment was not different between
controls and plants with portions of the frond removed. My harvest times would allow
for regeneration of fronds before the zoospores are shed in the fall. Additionally, I found
the net growth of Alaria to increase following a harvest. The lengths of both May and
June harvested plants, by August, were not significantly different from control lengths.
The lack of apparent growth of the controls is likely due to breakage of the frond rather
35
than reaching a terminal length. Larger (e.g. uncut) blades were probably more
vulnerable to breakage. The experimentally shortened plants are less subject to breakage
from wave action and rock abrasion which can cause catastrophic wounds in larger plants
(DeWreede et al 1992). Furthermore, the congener Alaria esculenta (L.) has been
demonstrated to grow throughout the year (Buggelin 1974) with growth pulses between
April and Late June (Buggelin 1977). Herbivory is not likely to contribute significantly
to the shortening of the control plants because the high concentration of phenolics in
growing Alaria marginata (Steinberg 1984; Duggins and Eckman 1997) probably results
in little grazing. The results comparing the biomass of experimental and control plots
suggest recovery within the growing season and a possibility for two harvest yields per
year.
The slower net growth of plants at South Cove is likely due to less nutrient input.
Upwelling along the Oregon coast is known to intensify south of Cape Blanco (Strub et
al 1987). This would increase the nutrient levels at Hooskanaden Creek above those of
South Cove. Microclimate variations can have significant impacts on local vegetation
(Begon et aI1996).
Removal of 50% of fronds from plots in the selective/method of harvest
experiments produced the highest recruitments, although the differences were not
statistically significant. Removing just the frond spares the sporophylls allowing
production of spores and increased reproduction. Furthermore, thinning adult fronds from
the plots increased the light penetration to juveniles allowing heightened growth. The
lower recruitment observed in plots where 50% of the algae present were removed at the
36
holdfast supports this argument. This treatment removed the sporophylls and therefore
lowered spore potential. Dispersal distance in marine algae is thought to be relatively
low (see Dayton 1973; Reed et al1988) so these treatments are likely to have localized
effects.
Laminaria setchellii
The life history of Laminaria is similar to that of Alaria except sporangia form on
the sporophyte frond. Vegetative growth is via an intercalary meristem (tom Dieck 1991;
Lee 1999). Again, the frond is collected by harvesters.
Net growth was slow in individuals following both May and June harvests. The
significant differences in plot biomass between harvested plots and controls indicate that
Laminaria was unable to recover during the same year it was harvested. This could be
attributed to the timing offrond removal. Kain (1963) and Luning (1969) found the
growth of Laminaria hyperborea to be punctuated by two phases: the fastest growth
occurring between January and June and a slow growth period between July and
December. In this study, both spring and summer harvests occurred during the end of the
period of fast growth, which could explain the minimal net growth observed in all
treatments. Harvesting Laminaria earlier in the year during the period of rapid growth
might ameliorate the effects seen in our May and June harvests.
Luning (1969), however, showed that second year L. hyperborea sporophytes .
assimilate reserve materials from the previous year's frond. Late summer harvests of
Laminaria could reduce growth in subsequent seasons due to the removal of the frond
37
containing this reserve material. Also, the lack of frond lengthening in our treatments
could affect reproductive potential because the sori form on the frond. Days with 8 or
less hours of light induce the formation of sori in L. saccharina (Luning 1988). Earlier
harvests may allow for greater frond lengthening and a possible increase in reproductive
potential. Luning et al (2000) found that frond removal can, however, prevent the
formation of sporangia which could negate any benefits of earlier harvests.
Despite these possibilities for lowered reproductive potential, recovery in the
subsequent year was evident by the lack of significant differences in total and germling
holdfast densities between May harvest, June harvest, and control plots. This supports
the conclusion that the tested times of harvest had no effect on the recovery of Laminaria.
Removing 25% of Laminaria present from plots resulted in the lowest total
holdfast density in the subsequent year. There was, however, no effect on germling
density. Species of Laminaria are able to produce large numbers of spores per plant
(Kain 1975; Chapman 1984). This allows a population to persist through disturbance
events such as harvesting (Chapman 1984) and ice scour (Heine 1989). The removal of
more plants from plots may open more space for early settling germlings, allowing them
to reach adult size in the following year. Chapman (1984) found high reproductive
pulses for two species of Nova Scotia Laminaria in all months except July. Additionally,
removal of fewer plants from the plots may be hindering the growth of juvenile
sporophytes through shading. Juvenile sporophytes of L. saccharina off Long Island
survived summer conditions only if they settled the previous autumn (Lee and Brinkhuis
1988). Late year thinning may facilitate an autumnal settlement event by freeing space
38
for new recruits. However, in this study germling densities were not significantly
different between treatments.
Fucus gardneri
Fucus displays a different life-history than the previous two brown algal species.
Gametes are produced by antheridia and oogonia that develop in conceptacles on the
receptacles of the adult thallus. Therefore, no gametophyte stage exists separate from the
parent frond. Conceptacles form under short day (8: 16 hr LD) conditions (Lee 1999) and
gametes are dropped near parent fronds to fertilize (Pearson and Brawley 1996). The
zygote grows into the adult thallus with apical growth (Lee 1999). The adult thallus is
harvested.
Following cutting Fucus failed to grow for the rest of the season. Cutting
removes the apical meristems preventing further net growth of the alga. Adventitious
growth was not observed. Harvesting removes the receptacles preventing conceptacle
formation and therefore reproduction. Leaving the holdfasts of harvested plants still
attached to the rock possibly limited the desiccation, thermal, and wave force stress on
germlings (Speidel 2001). This allowed for recovery to occur in plots harvested during
May. This is evident by the lack of significant differences between the biomasses of
control plots and those harvested in May. Recovery, however, is relatively slow because
the biomass of June harvest plots were significantly different from control plots. All
plots were indistinguishable in total and germling holdfast density one year following
treatment. Fucus distichus has been demonstrated to be reproductive throughout the year
39
and recruits through new settlement only (Ang 1991). Harvesting of large plants may
have freed space for more gerrnlings to settle. High densities of F. distichus germlings
have been demonstrated reduce mortality (Ang and DeWreede 1992).
The lack of significant differences in total and gerrnling holdfasts between the
control and selective/method of harvest experimental plots were maybe due to the
remaining adults protecting germlings from stressors. Speidel (2001) showed that
removal of up to 80% of Fucus adults from plots recovered within one year, however,
removal of 100% resulted in a significantly longer recovery period. A similar pattern
was seen in Fucus populations disturbed by oil spills (van Tamelen et a11997). Fucus
recovery is relatively rapid if a few adults survive the disturbance event (Speidel 2001).
The four experimental treatments in my study all left some adults still attached to the
rock which could have facilitated the recruitment of the germlings. It is important to
note, however, that reproduction can only occur in uncut plants. Harvesting at
commercial scales would reduce the reproductive potential of the population resulting in
lower recruitment and density. Kim and DeWreede (1996) compared Fucus distichus
recovery between three patch sizes where all algae were removed and found the
intermediate size of 1Ox 10cm produced the highest percent cover after 20 months. Our
plot sizes for Fucus were 20x20cm, suggesting a smaller harvest area may result in faster
recovery.
Mastocarpus papillatus
40
The complex life-history of Mastocarpus begins with macroscopic male and
female gametophytes (Lee 1999). The male releases spermatia to fuse with the
carpogonium to produce the second stage carposporophyte, which grows upon the female
gametophyte. The carposporophyte releases carpospores that germinate into the
tetrasporophyte stage. The tetrasporophyte of Mastocarpus forms a dark crust referred to
as the "petrocelis" stage. This stage releases tetraspores that geminate into male and
female gametophytes (Lee 1999). Alternatively, Mastocarpus can reproduce through an
apogamous life-history where carpospores geminate into the erect form (Polanshek and
West 1977). Vegetative growth is though apical cell divisions of filamentous axes (Lee
1999). Only the gametophyte stage is harvested.
Due to the removal of the apical meristems little net growth was observed in
harvested Mastocarpus. Removal of gametophyte fronds would lead to lowered
reproductive output because fewer spermatia would be formed. Also, the
carposporophyte generation is removed along with female gametophytes. The negative
effects on reproduction due to harvesting, however, may be mitigated by the
tetrasporophyte stage. Harvesting would have no direct impact on tetraspore production
which could replenish gametophyte stocks. Sussmann and DeWreede (2001) found
annual variations in abundance of the tetrasporophyte stage with peaks in the summer and
early autumn. This suggests a high tetraspore potential for Mastocarpus shortly after our
harvests would have cleared space for new recruits. This conclusion is supported by the
apparent recovery of Mastocarpus after both harvests. Lack of significant differences in
the biomasses of control versus experimental plots suggest recovery within the harvest
41
year. Furthermore, the mean percent covers of all treatments were not significantly
different one year after experimentation, suggesting recovery after one year's time.
Through natural breakage Mastocarpus may experience disturbances similar to
harvesting. Large fronds of the congener Mastocarpus stellatus are subject to removal by
drag forces during periods of high wave energy (Pratt and Johnson 2002). Masocarpus
papillatus does not increase the diameter of its stipe in proportion with frond size and,
therefore, larger thalli are more vulnerable to breakage (Carrington 1990). By manually
shortening the fronds, harvesting may lessen the consequences of drag forces during
winter storms allowing the basal disc to survive into subsequent years.
The experiments comparing different removal amounts and methods also
produced no significant differences in second year percent cover. This suggests recovery
within one year of these harvests. Space may have been opened for new recruits by
experimentally thinning plots allowing for the observed recovery.
Mazzaella splendens
The life-history of Mazzaella is similar to that of Mastocarpus described above.
Mazzaella growth is also the same as described above. The two algae differ, however, in
that the gametophyte and tetrasporophyte stages in Mazzaella are isomorphic and that an
apogamous life-history is not known (Lee 1999). Both the gametophyte and
tetrasporophyte stages of Mazzaella are collected by harvesters.
The lack of within-season net growth observed in harvested Mazzaella is
attributed to the removal of the meristems. These harvests likely removed both
42
gametophytes (with associated carposporophytes) and tetrasporophytes. This has the
potential to lower the population's reproductive potential significantly. However, the
differences in biomass of June harvested and control plots were not significant suggesting
recovery within the harvest season.
Mazzaella thalli typically senesce at the end of the autumn down to the basal disc
which is responsible for holding space for the subsequent year's holdfast and initiating
growth of the next year's blade (Hansen 1977). Our harvests were unlikely to have
effects lasting through the winter because the holdfast was spared. This is supported by
the lack of significant differences in the percent cover of experimental and controls plots
one year after treatment. Scrosati (1999) reported on harvest recovery of the congener M.
parksii (as M. cornucopiae) and showed complete recovery in early spring harvested
plants when the holdfasts were spared and suggested a high sustainable yield when only
thalli were cut. Harvesting at commercial scales may, however, lower the recovery
ability of Mazzaella since the absence of neighboring plants following extended harvests
would limit recruitment in cleared areas. Harvested individuals cannot contribute
significantly to reproduction therefore, recruitment must be from neighboring plants.
Removal of Mazzaella at the holdfast resulted in significantly lower percent cover
the following year. Loss of the perennial basal disc caused the alga to loose its space on
v
the rock and allowed the invasion of other organisms (Hansen 1977). Both frond
removal treatments were not significantly different from controls because the basal discs
were spared.
43
Limitations and Conclusions
These experiments did not assess the effects of harvesting on the associated
community. Pieces of macroalgae that break off of growing fronds enter the food web as
detritus. Duggins and Eckman (1997) showed Alaria and Laminaria to be an important
food source for invertebrates once the secondary metabolites had been leeched from the
frond. Harvesting would reduce this food source.
The findings in these experiments represent the first two years of a three year
study. The results to date suggest these species can support sustainable harvesting.
These data suggest that leaving the holdfast allows for the fastest recovery in most cases
and recovery is evident after one year. The biomass of all experimental and control plots
will be compared at the end of three years to fully assess recovery. Associated fauna will
be collected during this time and compared between treatments. These results will
provide data useful in drafting plans for the management of Oregon's algal resource.
44
BRIDGE I
The previous chapter examined the effects of different harvest times, amounts,
and methods. All species reached initial density after most treatments one year following
harvesting. Harvest time and amount had little effect on recovery. Sparing the holdfast
allowed for faster recovery in most cases. These data suggested that the marine algae of
Oregon can support a commercial industry. Chapter III uses the results from the harvest
experiments to recommend a management strategy that would protect Oregon seaweed
from overexploitation. I suggested harvest times, methods, and removal amounts to
reduce harvest impacts on the recovery of the five species examined.
45
CHAPTER III
PROPOSED MANAGEMENT RECOMMENDATIONS FOR THE
HARVEST OF FIVE MACROALGAL SPECIES ALONG THE
OREGON COAST
Here I present suggestions recommendations for the harvest management of the
five species discussed in the previous chapter. These suggestions are based on the data
collected during the first two years of a three year study. Data collected from the third
year may result in changed the following management strategiesrecommendations. In
addition, these recommendations may be inappropriate during years with anomalous
climate conditions. For example, the warm phase El Nino Southern Oscillations may
reduce nutrient input leading to longer recovery periods for harvested algae. I will begin
with general recommendations for the management of algal harvesting along the Oregon
coast and then suggest species-specific management strategies (Table l).
The macroalgae of Oregon can potentially support a commercial harvest. Strict
management, however, will be required to prevent overexploitation. Prior to issuing of
harvest permits, Oregon Parks and Recreation Department (OPRD) should survey the
coast and delineate areas suitable for harvest. These areas should support an abundance
of macroalgae. If they occur in state park boundaries, other criteria (e.g. preserving a
46
natural environment for park visitors) may be relevant but are not considered here. Algal
spore dispersal distance are often relatively small (see Daton 1973; Reed et alI988). T
therefore, I recommend harvests to occur along straight transect lines parallel or
perpendicular to shore through dense beds of target species. Based on the size of my
experimental plots, I recommend these transects should be 50cm wide and 50 meters long
with 100 meters between each harvest transect. Harvesting along transects would allow
spore dispersal into the harvested areas from neighboring plants.
To finance the cost of enforcement, OPRD might consider selling permits.
Applications for harvest should specify which species are to be harvested and where.
The permittee would be required to report wet weights of all harvested species, take
pictures of harvested areas before and after removal, and estimate percent of standing
crop harvested. These data would help the state further manage the harvest of marine
algae.
Alaria rnarginata
Alaria grows rapidly following harvesting. Data from harvest experiments
suggest that two crops of Alaria can be produced during one growing season. The timing
of the first harvest should be between..April and May to allow plants to recover before a
second harvest in August. My data suggests that Alaria can fully recover from two
harvests within one year. Alaria should be harvested by cutting the frond at least six
inches (;:::; 12cm) above the stipe. This allows for the meristems and the sporophylls to be
spared which facilitates recovery. The highest recruitment and plot densities were seen in
47
plots where the holdfasts and sporophylls were not removed. My experiments removed
68.6 kg (::::; 151 Ibs) of Alaria wet weight from a study site and full recovery was seen
within one year. James Jungwirth of Nature Spirit Herbs and Sea Vegetables, the sole
current permitee, harvests 400 Ibs of Alaria under an experimental commercial harvest
permit with no apparent impact in subsequent years. My plot sizes and harvest amounts,
however, are too small to suggest that any amount greater than what I took will have no
detectable impact.
Laminaria setchellii
Net growth of Laminaria was slow following harvesting. Laminaria should be
harvested only between March and May to allow for the intra-annual recovery of the
harvested individuals. Harvest experiments showed that the method of removal had no
measurable effect of removal method on recovery. The scale of my experiments,
however, may have been too small to detect significant effects of holdfast removal. It is
thereforeTo be cautious, I am recommendinged that fronds should be cut at least 6 inches
(::::; 12cm) from the stipe. I removed 46.5 kg (::::;102Ibs) of Laminaria wet weight from a
site and full recovery was evident within one year. Jungwirth is allowed 400 lbs under
his permit. My experiments found",gignificantly higher plot density following recovery
when larger amounts were50% of Laminaria were harvested in plots than when lesser
amounts were harvested. This result suggests that larger amounts could be taken without
affecting recovery. ,hData are not available, however, to recommend an upper limit of
harvest amount.
48
Fucus gardneri
Fucus failed to grow following harvesting since cutting removed the apical
meristems, preventing further growth of harvested individuals. Furthermore, harvesting
removed the reproductive structures of Fucus. Recovery, therefore, was dependent on
neighboring individuals. RIn this study, removal method had no measured affect on
Fucus,. hoHowever, previous work has shown that recovery was significantly longer
when all holdfasts were removed from a plot (Sspeidel 2002). Therefore, Fucus should
be harvested by cutting the frond at least six inches (z12cm) above the holdfast. My
experiments found no significant differences in biomass between May harvest and
controls plots, but did find significant differences between June harvest and control plots.
Therefore, I recommend Fucus be harvested only between April and May to facilitate
intra-annual recovery. I removed 7.3 kg (z16Ibs) wet weight of Fucus from a site
without measured effects. Jungwirth is allowed 800 lbs of Fucus annually. Fucus is
vulnerable to overexploitation because recovery is dependant on neighboring individuals
repopulating harvested areas. I therefore, cannot safely recommend harvest amounts
greater than those which I removed.
Mastocarpus papillatus
Harvesting of Mastocarpus removes the apical meristems preventing further
growth within the harvest year. However, I observed full recovery one year after
49
harvests. Biomass comparisons between May harvest, June harvest, and control plots
produced no significant differences. Therefore, I recommend Mastocarpus be harvested
between May and August. Removal method had no measurable affect on Mastocarpus
suggesting recovery can occur either by regrowth from spared holdfasts or settlement of
new recruits. Mastocarpus can be harvested by cutting the frond or pulling off the
holdfast. I removed 2.2 kg (::::4.8 lbs) wet weight of Mastocarpus from a site with no
detectable effect. I found no significant differences in recovery between removal
amounts suggesting greater amounts could be harvested without effect. ,hHowever,
more data are needed to set an upper harvest limit.
Mazzaella splendens
Harvesting removes the apical meristems of Mazzaella preventing further growth
within the harvest year. Additionally, harvesting removes all life-history stages of
Mazzaella. I found no significant differences in biomass between June harvest and
control plots. This suggests Mazzaella can be harvested between June and August and
recover intra- and inter-annually. The removal of Mazzaella holdfasts resulted in
significantly lower percent cover one year after harvest. Therefore, I recommend
Mazzaella should be cut at least 4.inches (:::::8cm) above the holdfast. Mazzaella should
not be harvested in such a way that the holdfast is removed. I was unable to test the
effects of different harvest amounts for Mazzaella and therefore, cannot make
recommendations as to harvest limits.
Table 1. Recommended Management Strategies for the Harvest of Five Macroalgal Species of Oregon.
Species Harvest time Harvest method Harvest amount per transect
Alaria marginata April to May Cut 6 inches above stipe 150 pounds/year
August
Laminaria setchellii March to May Cut 6 inches above stipe 100 pounds/year
Fucus garneri April to May Cut 6 inches above holdfast 15 pounds/year
-:
Mastocarpus papillatus May to August Cut frond or pull holdfast 5 pounds/year
Mazzaella splendens June to August Cut/tear 4 inches above holdfast No Data
VI
o
51
BRIDGDE II
The previous two chapters dealt with effects of seaweed harvest and possible
management strategies,. Chapter II examininged the effects of seaweed harvest on the
harvested species only. Potential impacts on the associated community were not assessed
and. Accordingly, the management recommendations presented in Chapter III do not
consider those possible impacts. Examination of associated communities is needed
before any potentialfull effects from harvesting can be elucidated.
Chapter IV provides a first step in understanding the community dynamics of
marine macrophytes. The following chapter gives a detailed analysis of the epiphytic
diatom community upon Mastocarpus papillatus (c. Agardh) Ktitzing. Additionally, I
examine temporal changes in this community structure over a growing season and
examine the role of grazing by Littorina keenae in changing epiphytic community
structure. These data will allow comparison of epiphytic communities to be used as an
additional metric to assess recovery of M. papillatus after harvesting. The information is
also valuable in itself. Epiphytic communities in estuaries have been well studied, but
similar communities in the rocky -intertidal are virtually unknown.
52
CHAPTER IV
ANALYSIS OF THE EPIPHYTIC DIATOM COMMUNITY UPON THE
MACROALGA Mastocarpus papillatus (C. Agardh) Ktitzing
Introduction
Micro-organisms have often been used as metrics to assess various environmental
factors. Fecal coliforms are common indicators of sewage contamination and bacterial
diversity has been used to test restoration success (Milbrandt 2003). Epiphytic diatoms
are used as biomonitors of water quality (Kelly et al 1998) and have been used to assess
habitat fidelity (Winter and Duthie 2000), disturbance (Luttenton and Rada 1986), and
paleolimnological conditions (Christie and Smol1993). Diatoms are good bio-indicators
because the silicified frustules are taxonomically distinct and easily preserved and
variations in community composition track environmental conditions (Christie and Smol
1993). Epiphytes are ideal indicators of nutrient loading because they quickly respond
via changes in their community stf4,9ture. Experiments have shown that the epiphytic
assemblage of Zostera marina L. changed following nutrient addition both in the
laboratory (Coleman and Burkholder 1994) and in situ (Coleman and Burkholder 1995),
making these epiphytes good indicators of eutrophication.
53
Epiphytic diatoms are also important components of estuarine communities
because of their significant role in the food web. The primary production of algal
epiphytes has been estimated at times to be greater than that of the substrate providing
seagrasses (Morgan and Kitting 1984; Kitting et al 1984; Mazzella and Alberte 1986).
Epiphytic diatoms also have high nutritional value and likely lack the phenolic
compounds found in seagrasses that inhibit herbivory (Zimmerman et al 1979; Harrison
1982). Studies have shown epifaunal grazers derive more nutrition from algal epiphytes
than seagrasses (Kitting et a11984; Harrison 1982; Howard 1982). These properties
make epiphytes important determinates in epifaunal abundances and assemblages (Hall
and Bell 1988; Nelson 1997).
Like estuaries, the rocky intertidal is a dynamic and productive system, yet
epiphytic communities have been less well studied. Macroalgae are the dominate
vegetation of the intertidal zone, and they provide substrate for epiphytic colonizers.
Despite their importance, algal epiphytes in rocky bottom systems have been the
subject of few ecological investigations. Belegratis et al (1999) examined the epiphytic
community of Cystoseira species and Christie et al (1998) assessed epiphyte
recolonization following kelp harvest. However, both these studies focused on macro-
epiphytes. Additionally, epifaunal abundance on marine macroalgae has been linked to
epiphytic biomass (Hagerman 1966; Gunnill 1982; Johnson and Scheibling 1987). Yet,
to date no studies have attempted to quantify and describe the microepiphytic community
of intertidal macroalgae.
54
Given the use of epiphytic diatoms in assessing environmental factors (i.e., water
quality, habitat fidelity, disturbance) and their importance in energy cycling (O'Quinn
and Sullivan 1983), it is important to establish a community baseline in the rocky
intertidal. This study identified and catalogued the epiphytic diatom community on the
macroalga Mastocarpus papillatus (c. Agardh) Ktitzing throughout a growing season.
These data may be useful in assessing recovery from disturbance events such as
trampling, harvesting, or oil spills. Furthermore, this work provides a first crucial step in
using these organisms as a nutrient indicator in open coastal areas.
Materials and Methods
Diatom communities were analyzed from dried samples of Mastocarpus
papillatus (Rhodophyta) archived from a harvest study. Three monthly replicates were
analyzed beginning in May 2002 and continuing through September 2002. All samples
were collected from Lone Ranch Creek (42°05.98'N, 124°20.91'W, Fig. 19) in Samuel H.
Boardman State Park, Oregon, USA from the same cove and tidal level. Collected M.
pappillatus were briefly rinsed in freshwater to remove all macrofauna and then dried in
an oven set at 60°C for 14 days.
Initial comparisons of epipho/te abundance between rinsed samples (dipped in
freshwater) and unrinsed samples were made. Aliquots from these samples were counted
using a hemocytometer. Comparisons were analyzed by a student's T-test. No
significant difference was found in epiphytic abundance between rinsed and unrinsed
55
OREGON
Pacific
Ocean
Figure 19: Location of Lone Ranch Creek. All samples of Mastocarpus papillatus were
collected at this site.
56
samples (t= 3.18, p<0.468). Rinsing Mastocarpus in freshwater had no effect on
epiphytic abundance.
Dry weight of Mastocarpus papillatus was correlated with surface area so surface
area estimations could be made from archived samples. Samples for analysis were
collected on 6th July, 2003. I assumed that this correlation would not differ between
months and years. Surface area was measured using the program OPTIMUS (Optimus
Corporation) and correlated with known sample weights. Measured surface area was
doubled to account for both sides of the frond. Surface area was natural log transformed
and correlated with dry weight. There was a strong correlation between the natural log of
surface area and the dry weight of Mastocarpus (r2=0.881, n=108, p< 0.0001, Fig. 20).
Algal dry weight is a good predictor of surface area.
The bumpy surface of Mastocarpus was not scraped to remove algae. Rather,
three 0.5g replicate samples of Mastocarpus from each month were chemically digested
by submergence in concentrated KMn04 for 14hrs. Equal portions of IBM HCI was
added to the solution and gently warmed at 75°C in a sand bath for 4hrs. Samples were
washed six times by centrifuging at 15,000 rpms for 20 minutes or until the solution pH
was neutral and diluted with distilled water to 40mL. One milliliter aliquots from each
replicate were analyzed. Ten slides with 100~L each per sample were mounted in
NAPHRAX. Transects were counted across the cover slip of each slide. Fifty valves
were identified and counted per slide so that each replicate was rarefied to 500
individuals. Diatoms were identified according to Hustedt (1962), Hendey (1964),
Ricard (1987), Round (1990), and Hartley et al (1996). The area of transects and the
5...,..------------------------,
O~-_+_-_.-__r--,.___-_,__-_.-_.,.--,.___-_,__--l
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
Dry Weight (g)
Figure 20: Correlation between the In of Surface Area and the Dry Weight of
Mastocarpus papillatus (r= 0.881, n=108, p<O.OOOl).
57
58
volume on each slide was used to calculate diatom abundance per mm2 on the host alga.
The total number of all araphid and centric species were divided by two and either the p
or r-valve was counted for raphid species to avoid over estimation.
Changes in epiphytic abundance were analyzed with a one-way ANOVA with
different months or days as treatments. A Bonferroni post-hoc test was performed on all
significant results. A non-parametric Kruskal-Wallis test was used if the assumptions
necessary for an ANOVA were violated.
Mastocarpus blades were sampled intensely between 15 July, and 18 July, 2003.
Three replicates were collected each day for analysis. All samples were collected from
the site described above and treated in the same manner. Analysis was the same as
described above. This was done to ensure that any patterns seen over a monthly scale
were not just an artifact of the day samples were collected.
Changes in epiphytic diversity were measured with the Shannon-Weiner index.
;
H =-L(Pi*lnPi)
;=1
where Pi represents the proportion of the ith species in the sample. Differences in
epiphytic diversity were measured using an ANOVA with month or day as the treatment
factor. Changes in epiphytic communities were measured by creating a similarity index
using the Bray-Curtis coefficient where Yij represents the ith row (species) and jth column
(species abundance) in the generated data matrix (Clarke and Warwick 2001). Non-
Sjk =100
p
Ilyy- Yik!
l __i~~I _
p
I(Yif + Yik)
i~1
59
metric Multi Dimensional Scaling (MDS) plots and cluster diagrams were made from 4th
root transformed similarity matrices. One-way ANOSIMs were used to test for
differences in epiphytic communities across different months and different days. All
univariate analyses were performed using the statistical software package Statistica 6.0
(Statsoft). Multivariate statistics analyzed with the statistic package PRIMER E (Clarke
and Gorley 2001).
Littorina keenae removed from samples collected between 15 and 18 July 2003
were analyzed for ingested diatoms. Snails were placed in MgCh and all soft body tissue
was removed and chemically digested as described above. Littorine gut contents were
qualitatively sampled and mounted in NAPHRAX. Diatom valves were counted as
describe4 above and compared to the ambient epiphytic community using the same
multivariate statistical methods.
Results
A total of 38 diatom taxa were identified from Mastocarpus fronds (Appendix B,
Table 8). Cocconeis scuttelum was the most abundant species in all samples, however,
its abundance increased over the growing season. The abundance of C. scuttelum (Fig.
21) was lowest in May with a mean of232.6 (±27.8 S.E.) per rarified sample, and
increased to its highest value of 380.3 (±14.3 S.E.) in July.
60
450
400
I •rfJ(L) 350;>.......~;>
"'l
...... 300~
:;::
c:J
'"'
'"'c:J 250U
200
150
May June July August September
Month
Figure 21: Mean Numbers of Cocconeis scuttelum Valves Counted per Sample. Error
bars show one standard error from the mean.
61
Abundance differed significantly during the 2002 growing season (X2=12.32,
p=0.015, Fig. 22a). Abundance was the lowest in May with 79.5 cells per mm2 (± 20.3
S.E.) and peaked in July with 3361.2 cells per mm2 (± 87.9 S.E.). Abundance declined
slightly during August and September. Shannon-Weiner diversity (H') also differed
significantly (F=9.889, p< 0.0017, Fig. 22b). Diversity peaked in May with a mean
H'=1.907 ±O.l4 S.E. and reached a low in July (H'=.9688 ±O.l4 S.E.). Post-hoc analyses
revealed significant differences between May diversity and July, August, and September
diversity. The four day intensive sampling period yielded no significant differences in
epiphytic abundance and diversity (F=0.433, p=0.735, Fig. 23a and F=1.35, p=0.325, Fig.
23b, respectively).
The MDS plot and cluster diagram showed that samples from both May and June
grouped closely (Figs. 24a and 24b). July, August, and September samples yielded no
distinct grouping in the MDS. The ANOSIM comparing epiphytic communities across
months produced a global R of 0.370 (p=0.006), suggesting distinction between monthly
communities. Pair-wise testing found a strong distinction between the epiphytes of May
and July (R=0.889). This was further supported by the May and June replicates grouping
closely and independently. The May community was also distinct from August
(R=0.741). Other pair-wise tests failed to produce significant differences between
communities sampled during a month. There was little distinction between communities
sampled on consecutive days (R=0.275, p=0.019, Fig. 25a).
62
4000..,.---------------------,
aI
o.l----'.F---...,.----r-----.,------,,.---
3000
N
I
S
S 2000
*
..:!J
di
U
1000
May June July
Month
August September
2.2
,.-... 2.0~
'--'
;>, 1.8
.-:::
(/)
...
!I.l
>- 1.6
0
... 1.4!I.l
t::
'0)
~ 1.2
I !t:: ! !0 1.0t::§.c b(/) 0.8
0.6
May June July August September
Month
v
Figure 22: Epiphytic Diatom Patterns over the 2002 Growing Season. Mean epiphyte (a)
abundance and (b) diversity is shown with data points. Error bars show one standard
error from the mean.
63
3000
2800
f~ 2600E
E
*rfJ
-Q) 2400
U
2200
a
2000
Tue 15 Wed 16 Thu 17 Fri 18
July
1.4
e:::--
6 1.3
>.
+-'
'iii 1.2...
(])
>
i:S 1.1
...
(])
c 1'Q) 1.0 I~IC 0.90Cc<U 0.8J::
Cf) b
0.7
Tue 15 Wed 16 Thu 17 Fri 18
July
......
Figure 23: Epiphytic Diatom Patterns over Four Consecutive Days in 2003. Mean
epiphyte (a) abundance and (b) diversity is shown with data points. Error bars show one
standard error from the mean.
Stress: 0.11
July
64
August
August
September
August
July
Septemb r
September
July
a
60
;>-
.....
.-~ 70
.-S
.-r/)
r/)
.- 80.....I-<
;:l
U
I
;>-
ro
I-< 90~
100
>- >- >- >- >- Q; >- tltl Q; Q; Q) Q) Q) tl:; :; c
'" '"
c c
'"
:;::J
.0 .0 ::J ~ ~ ::J ::J ~ ::J .0 ::J..., Cl E E ..., Cl E ..., Cl::J ..., ..., ..., ::J ::J
« ~ ~ « ~ «
a. a. a.
Q) Q) Q)
UJ UJ UJ
v b
Figure 24: Epiphytic Community Patterns in 2002. Communities are shown with (a)
MDS plot and (b) cluster diagram. Both figures are based on Bray-Curtis similarty
matrices from 4th root transformed data.
65
Stress: 0.14
7/16
7/17
7/15
7/18
7/17
7/16 7/16
7/17 7/18
7/15 7/18
7/15
7/15
7/17 7/15 7/18
7/17 Littorine 7/15
7/16 7/16
Littorine 7/15 7/15
a
Stress: 0.15
7/18
7/18 7/17
7/16 b
Figure 25: MDS Plots of the Epiphytic Communities from 2003. Communities are from
(a) four consecutive days in 2003 and (b) with littorine gut diatom community
superimposed.
66
The analysis of littorine gut diatoms showed no evidence of selective feeding.
The gut diatom community grouped closely with the ambient epiphytic diatom
community from the same sampling day (Fig. 25b).
Discussion
The epiphytic community of Mastocarpus changed over the growing season
between May and September. The changes in Mastocarpus epiphytes were directional in
the early portion of the season with distinct May and June communities. However,
distinct monthly communities broke down beginning in July. That is, the community
distinctions broke down when abundance increased and diversity decreased. The
decrease in diversity was attributed to the dominance of Cocconeis scuttelum, which
comprised nearly eighty percent of valves identified in the July, August, and September
samples. This dominance would, in turn, increase the index of similarity between
samples and obscure distinctions between monthly communities.
Seasonal succession has been demonstrated in planktonic diatom communities
(Sancetta 1989; McQuoid and Hobson 1995; Hobson and McQuoid 1997; Tilstone et al
"J
2000; Rousseau et al 2002). A host of biotic and abiotic factors have been attributed to
drive these successional processes such as silica availability (Rousseau et al 2002),
diatom resting stages (McQuoid and Hobson 1995), and nutrient availability
(Kamykowski and Zentara 1985). These patterns have been observed in many places
67
around the globe and can be relatively predictable. Changes in attached diatom
communities have received less attention. Amspoker and McIntire (1978) reported on
the distribution of intertidal diatoms in the Yaquina estuary, Oregon and found sediment
size and salinity to be determinates in species composition, explaining community
differences between sites. Salinity and sediment size are not responsible for the epiphytic
patterns observed upon Mastocarpus at Lone Ranch Creek. There is minimal freshwater
input so salinity is unlikely to change and the substrate was constant between samples.
Epiphytic diatoms communities in the Yaquina estuary were also found to be strongly
determined by desiccation as well as biotic factors such as host-epiphyte interactions
(McIntire and Overton 1971). Desiccation stress should vary little between sampling
dates because between the spring and fall equinox all extreme tides occur during the
daylight and all samples were taken from the same tidal height. Interactions with
Mastocarpus could possibly be an important factor structuring the epiphytic community.
However, since the fronds displayed little net growth between May and September,
possible interactions should not vary between sampling dates. Any possible interactions
are likely minor because the quality (size, thickness, stipe strength) of Mastocarpus
remained unchanged between May when the epiphyte load is low and September when
there was high epiphytic abundance. A seasonal pattern is likely to exist in this system
because the basal disc of Mastocarpus is perennial, but the frond is annual and, therefore,
only available for colonization during the growing season.
With abiotic factors such as salinity, dessication, and substrate unlikely to be
strong determinates in shaping these communities, the question remains: what forces the
68
observed changes? Grazers have been demonstrated to be important in altering the
trajectories of algal succession in freshwater streams (Steinman et al1989); benthic algal
biomass decreased in streams subjected to herbivory. Furthermore, herbivory was
responsible for slowing the natural succession of these communities. Similar results have
been reported in intertidal diatoms from the Oregon coast where littorines and limpets
reduced benthic diatom biomass significantly during the summer but not in the winter
(Castenholz 1961). Experimental enclosures showed that littorines were able to clear
diatom films and keep areas nearly denuded of benthic rnicroalgae (Castenholz 1961).
Diatoms are known to be a principle constituent of littorine diets (Castenholz 1961;
Davies and Beckwith 1999; Worm and Sommer 2000). Thus, herbivory may be a strong
determinate in the observed patterns of Mastocarpus epiphytes. My gut content results
confirmed that Littorina keenae does feed on benthic diatoms. The results suggested,
however, that they feed indiscriminately as evidenced by the lack of distinction between
the epiphytic and gut diatom communities from the same day. The patterns observed by
Steinman et al (1989) and Castenholz (1961) differed from mine in that the abundance of
the Mastocarpus epiphytic community increased in the presence of herbivory. Herbivore
density was not measured during the sampling days so community changes cannot be
attributed solely to herbivore density. Exclusion experiments where littorines and other
herbivores are kept from Mastocarpus fronds would accurately test the hypothesis that
metazoan herbivory is shaping this epiphytic community. This would not eliminate the
possibility that micrograzers are exerting pressure and driving community change.
69
Admiraal (1977) found grazing by ciliates were responsible for the change in species
composition of benthic diatoms in a Wadden Sea mudflat.
Steinman et al (1989) found that a species of Cocconeis became the most
abundant benthic species following increased herbivore density. The genus Cocconeis is
a common epiphytic species with a global distribution (Hendey 1964). De Stefano et al
(2000) found Cocconeis to be the dominate epiphytic genus upon Posidonia oceanica
(L.) Delile in the Mediterranean Sea. Cocconeis was also the dominate genus in North
Brittany mudflats during the winter, but was less dominate during the summer (Riaux-
Gobin 1991). Conversely, in this study C. scuttelum was common in all monthly samples
of Mastocarpus, but reached its highest abundance in July. Therefore, it is reasonable to
assume that C. scuttelum is a successful competitor in this system. It may be more
efficient in occupying space, acquiring nutrients and light, and surviving adverse
conditions. Hudon and Bourget (1983) reported on the low light tolerance of the genus
Cocconeis, and C. placentula is typically considered to be a shade specific species (Tuji
2000). Dense periphyton mats have been shown to induce physiological stress on
individuals deeper in the mat through nutrient attenuation (Meulemans and Roos 1985;
Hudon et al 1987).
Stevenson et al (1991) hypothesized that succession in a Kentucky stream was
"J
driven by late succession species reducing available nutrients to a level where early
succession species can no longer survive, and then out competing them. This may be the
most likely explanation for the increase in abundance of C. scuttelum upon Mastocarpus
between May and August. Nutrients are usually high in May when C. scuttelum is
70
present but in lower numbers. C. scuttelum may reduce the nutrient pool to levels where
other species can no longer persist during periods between local upwelling events. The
Oregon coast experiences intermittent periods between strong north winds and calm
conditions (Huyer 1976). The north winds drive upwelling, which increases the nutrient
pool (Mann and Lazier 1996). These nutrients are typically depleted by phytoplankton
during the downwelling that occurs between upwelling events. This intermittent nutrient
input may allow C. scuttelum to gain a competitive advantage and dominate in the
periphyton. This hypothesis, however, remains untested. Microcosm experiments with
mixed species and various nutrient regimes could be performed to assess this possibility.
The forces shaping the community dynamics of Mastocarpus epiphytes and for
the mid summer increase in C. scuttelum remains unclear. However, the pattern of
increasing biomass and decreasing diversity is not unique to this system. Diversity often
decreases with increasing latitude and altitude. Communities at intermediate latitudes are
dominated by fewer species well suited to prevailing conditions. Succession generally
follows a path from a low diversity of early colonizers to a stable community with high
relative diversity. However, climatic variations may lead to a climax community with
lower diversity (Begon et al 1996).
71
CHAPTER V
CONCLUDING SUMMARY
There were two objectives of this thesis: (l) to explore possible impacts of
commercial seaweed harvest in Oregon and to recommend strategies to manage the
resource, and (2) describe the epiphytic diatom community of Mastocarpus papillatus.
Data from these experiments were needed to prevent the overexploitation of Oregon's
wild algae stocks. This work provides a first step in developing a sustainable commercial
seaweed harvest industry in Oregon.
The goals of the experiments from Chapter II were to compare algal recovery
following harvesting during different seasons, harvesting different amounts, and different
harvest methods. The data suggested that all five species should be harvested in the
spring. Only Alaria marginata supported a second late seasonal harvest. My
experiments found no measurable effect of different harvest amounts, and, with the
exception of M. papillatus, recovery increased when the holdfast was not removed. The
results from these experiments suggested that Oregon's seaweed can support a
v
sustainable commercial harvest if managed correctly as outlined in Chapter III.
The experiments from in Chapter IV catalogued the epiphytic diatom community
upon M. papillatus and chronicled community changes over a growing season. A distinct
pattern was seen starting with relatively high epiphytic epiphyte diversity and low
72
abundance early in the season shifting to relatively low diversity and high abundance in
the mid to late summer. Similar patterns were not seen when communities were
compared over four consecutive days. These patterns are were attributed to the mid
season dominance of the diatom species Cocconeis scuttelum. Comparisons of gut
contents from the dominant epiphyte grazer Littorina keenae to ambient epiphyte
communities eliminated herbivory as one possible process controlling the dominance of
C. scuttelum. C. scuttelum may out out-compete other epiphytes leading to its dominance
in this system.
APPENDIX A
STATISTICAL TABLES FROM CHAPTER II
73
74
Table 2. Man-Whitney U Tests Comparing Mean Lengths of Harvested and Unharvested
Algae in August 2002.
Alaria setchellii
Hooskanaden Creek
May Harvest vs. Control
June Harvest vs. Control
South Cove
June Harvest vs. Control
Laminaria setchellii
Hooskanaden Creek
n
5
5
n
10
U
34.0000
26.0000
U
24.0000
p
0.6203
0.5217
p
0.000364
n U P
May Harvest vs. Control 4 0.00 0.0017
June Harvest vs. Control 4 0.00 0.0055
South Cove
v
Un p
May Harvest vs. Control 7 25.00 0.0080
June Harvest vs. Control 22 1.00 0.0000
Table 2. continued.
Fucus gardneri
May Harvest vs. Control
June Harvest vs. Control
Mastocarpus papillatus
May Harvest vs. Control
June Harvest vs. Control
Mazzaella splendens
June Harvest vs. Control
n
4
4
n
5
4
n
5
u
0.00
0.00
u
0.00
0.00
u
2.00
p
0.0021
0.0018
p
0.0045
0.0014
p
0.0001
75
Table 3. ANOYA Source Tables Comparing Biomass of Season of Harvest Plots in
2002.
Alaria marginata
Hooskanaden Creek
76
Source
Harvest Month
Error
South Cove
Source
Harvest Month
Error
Laminaria setchellii
Hooskanaden Creek
dJ.
2
5
d.f.
1
5
MS
23076.1
39428.0
MS
4760
20071.6
F
0.58527
F
0.23717
p
0.5910
p
0.646857
Source d.f. MS F P
Harvest Month 2 1263.2 23.069 0.0008
Error 7 54.757
South Cove
",..
Source dJ. MS F P
Harvest Month 2 9943.9 3.81364 0.076
Error 7 2607.5
Table 3. continued.
Fucus gardneri
.
Source
Harvest Month
Error
Mastocarpus papillatus
Source
Harvest Month
Error
Mazzaella splendens
Source
Harvest Month
Error
dJ
2
7
d.f.
2
6
dJ.
1
5
MS
663196
89323
MS
39.817
176.656
MS
34.706
35.582
F
7.4247
F
0.22539
F
0.97537
p
0.0186
p
0.8047
p
0.3687
77
78
Table 4. ANOVA Source Tables for Total and Germling Holdfast Density of Season of
Harvest Plots in 2003.
A/aria marginata
Hooskanaden Creek
Total Holdfasts
Source dJ. MS F P
Harvest Month 3 301.026 0.438671 0.7309
Error 9 686.222
Germling Holdfasts
Source d.f. MS F P
Harvest Month 3 210.906 0.267269 0.8474
Error 9 789.117
South Cove
Total Holdfasts
Source
Harvest Month
Error
Germling Holdfasts
Source
Harvest Month
Error
d.f
2
9
d.f.
2
9
MS
192.952
245.344
MS
43.369
68.881
F
0.786457
F
0.629623
p
0.4844
p
0.5547
Table 4. continued.
Laminaria setchellii
Hooskanaden Creek
Total Holdfasts
Source d.f. MS F P
Harvest Month 3 24.587 0.5783 0.6424
Error 10 42.517
Germling Holdfasts
Source d.f. MS F P
Harvest Month 3 15.1111 0.66084 0.5947
Error 10 22.8667
South Cove
Total Holdfasts
Source d.f. MS F P
Harvest Month 3 172.91 1.7440 0.2449
Error 7 99.14
Germling Holdfasts ,,~
Source d.f. MS F P
Harvest Month 3 51.1111 0.87548 0.4980
Error 7 58.3810
79
Table 4. continued.
Fucus gardneri
Total Holdfasts
Source d.f. MS F P
Harvest Month 3 31.504 0.41870 0.7435
Error 10 75.242
Germling Holdfasts
Source d.f. MS F P
Harvest Month 3 2.5159 0.29368 0.8291
Error 10 8.5667
Mastocarpus papillatus
80
Source
Harvest Month
Error
Mazzaella splendens
Source
Harvest Month
Error
d.f.
3
7
d.f.
2
5
MS
1498.58
683.02
MS
635.35
133.43
F
2.19404
F
4.7616
p
0.1766
p
0.06955
Table 5. Factorial ANOVA Source Tables for Total and Germling Holdfast Density of
Selective/Method of Harvest Plots in 2003.
Alaria marginata
Hooskanaden Creek
Total Holdfasts
Source d.f. MS F P
Removal Method 1 13.762 0.09355 0.7660
Removal Amount 2 133.962 0.91068 0.4332
Method*Amount 2 534.115 3.63097 0.0652
Error 10 147.100
Germling Holdfasts
Source d.f. MS F P
Removal Method 1 0.21066 0.05191 0.8243
Removal Amount 2 2.90917 0.71694 0.5117
Method*Amount 2 20.4228 5.03299 0.0307
Error 10 4.05779
South Cove
Total Holdfasts
Source dJ. MS F P
(S
Removal Method 1 26.694 0.10040 0.7573
Removal Amount 2 78.935 0.29689 0.7489
Method*Amount 2 123.432 0.46426 0.6404
Error 11 265.871
81
Table 5. continued.
Germling Holdfasts
Source d.f. MS F P
Removal Method I 0.1111 0.001732 0.9676
Removal Amount 2 13.7225 0.213856 0.8107
Method*Amount 2 107.5191 1.675622 0.2316
Error 11 64.1667
Laminaria setchellii
Hooskanaden Creek
Germling Holdfasts
Source d.f. MS F P
Removal Method 1 12.9643 0.32752 0.5798
Removal Amount 2 24.1295 0.60959 0.5626
Method*Amount 2 10.3449 0.26134 0.7751
Error 10 39.5833
Fucus gardneri
Total Holdfasts
Source d.f. MS F P
"J
Removal Method 1 1.3444 0.07401 0.7917
Removal Amount 2 13.2365 0.72861 0.5090
Method*Amount 2 9.4032 0.51760 0.6127
Error 9 3.83333
82
Table 5. continued.
Germling Holdfasts
Source d.f MS F P
Removal Method 1 5.87778 1.53333 0.2469
Removal Amount 2 3.45721 0.90188 0.4395
Method*Amount 2 9.60135 2.50470 0.1365
Error 9 3.83333
83
Table 6. Kruskal-Wallis Test Results from Selective/Method of Harvest Plots of
Laminaria setchellii at Hooskanaden Creek. Results are for total holdfast density only.
84
Source
Removal Method
Removal Amount
d.f.
1
2
0.2539683
7.8666667
p
0.6143
0.0196
85
Table 7. ANOVA Source Tables for Plot Density of Selective/Method of Harvest Plots
in 2003.
Laminaria setchellii
South Cove
Total Holdfasts
Source
Treatment
Error
Germling Holdfasts
Source
Treatment
Error
d.f.
4
7
d.f.
4
7
MS
616.77
285.60
MS
12.2083
20.8333
F
2.15960
F
0.586
p
0.1760
p
0.6834
Mastocarpus papillatus
Source d.f. MS F P
Treatment 4 1694.09 2.08647 0.1652
Error 9 811.94
,,"
Mazzaella splendens
Source dJ. MS F P
Treatment 3 865.30 16.5766 0.0050
Error 5 52.20
86
APPENDIXB
SUMMARY OF EPIPHYTIC DIATOM SPECIES ABUNDANCE OVER THE 2002
GROWING SEASON
Table 8. Summary of the Mean Relative Abundance of Mastocarpus Diatom Epiphytes Collected and Counted During
the 2002 growing season. Estimations of relative abundance are indicated as follows: X =absent (0%), R =rare
«1 %), C =common (1-10%), F =frequent (10-50%), and D =dominant (>50%).
Sample Month
Taxon May June July August September
Achnanthes brevipes Agar{ih X X X X R
Achnanthes groenlandica Cleve R R R X R
Achnanthes spp.1 X R R R R
Amphora exigua Gregory R X X X X
Berkeleya rutilans (Trentepohl ex Roth) Grunow X R X X X
Berkeley spp.1 X X X X R
Cocconeis califomica Grunow F F F F F
Cocconeis clandestine A. Schmidt R C R R R
Cocconeis costada Gregory C C R R R
Cocconeis scuttelum Ehrenberg F D D D D
00
-.J
Table 8. continued.
Sample Month
Taxon May June July August September
Cocconeis speciosa Gregory C R X R R
Cuneolus skvortzowii (Nikolaev) Medlin R R R R R
<-Fragilaria striatula Lyngbye X R R R X
Gomphoseptatum aesuarii (Cleve) Medlin C R C C C
Licmophora spp. 1 R R X X R
Navicula directa (Wm. Smith) Ralfs in Pritchard C R X R X
Navicula distans (Wm. Smith) Schmidt C C R R R
Navicula spp. 1 X X X R X
Navicula spp. 2 R R R R R
Navicula spp. 3 X R R R R
Navicula spp. 4 X R X X X
00
00
Table 8. continued.
Sample Month
Taxon May June July August September
Navicula spp. 5 R R R R R
Navicula spp. 6 R R R X R
Navicula spp. 7 '( X X R X X
Nitzschia frustulum (Kutzing) Grunow in Cleve R R R R R
etGrunow
Opephora marina (Gregory) Petit C C R C C
Opephora pacifica (Grunow) Petit C C C C R
Parlibellus delognei (Van Huerck) Medlin R R R X R
Pseudogomphonema kamtschaticum (Grunow) C C R R R
Medlin
Skeletonema costata (Greville) Cleve R X X X X
Thalassionema nitzschioides (Grunow) C C C R R
Grunow ex Hustedt
00
I.D
Table 8. continued.
Sample Month
Taxon .May June July August September
Thalassiosira spp. 1 R R X X X
Thalassiosira spp. 2 R X X X X
"-Unknown 1 R X R X R
Unknown 2 R X X X X
Unknown 3 X X R R X
I.D
o
91
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